1. Field of the Invention
The invention relates to an image forming apparatus and an image forming method.
2. Description of the Related Art
Conventionally, there is known a technology for simultaneously reading an image of a front surface and an image of a back surface of a document and sequentially transferring the read image data to main memory. For example, Japanese Patent Application Laid-open No. 2005-236577 discloses an image forming apparatus having a first image data reading unit for reading an image of a front surface of a document, a second image data reading unit for reading an image of a back surface and capable of variably setting each of the transfer speed of first image data (image data of the front surface of the document) read by the first image data reading unit and the transfer speed of second image data (image data of the back surface of the document) read by the second image data reading unit.
Here, in Japanese Patent Application Laid-open No. 2005-236577, in order to reduce a time length until the transfer of the image data is completed, there is assumed a case that the first image data read by the first image data reading unit is transferred line by line with a line period (every time when a time length required to read the image data corresponding to one line of the document has passed), whereas the second image data read by the second image data reading unit is transferred line by line continuously and asynchronously to the line period. Incidentally, the transfer destination of each of the first image data and the second image data is main memory connected to a controller via a bus. In this case, the second image data is continuously transferred line by line. Therefore, when the second image data is transferred, the bus (data transfer path) between the controller and the main memory is continuously occupied until the transfer of the second image data has been completed. Accordingly, the second image data transferred to the main memory cannot be transferred to other device (auxiliary memory and the like) connected to the controller. That is, a secondary transfer cannot be executed.